The present invention relates generally to anti-siphoning devices for fluid containers and more specifically to an improved anti-siphoning device for use in the fill pipe of a fuel tank.
With the relative scarcity and expense of fuel, the siphoning of fuel from fuel tanks has greatly increased. Efforts have been made to provide locks or other securing devices to the cap of the fill pipe. Similarly, efforts have been made to provide an anti-siphoning device within the fill pipe to prevent the insertion of a tube into the tank such that fuel may be siphoned therefrom. A relatively expensive anti-siphoning device is illustrated in British Specification No. 739,386 having a fill tube closed at the bottom and secured to the fill pipe of the tank by a collar which includes a screw engaging the interior of the fill pipe. Another anti-siphoning device is illustrated in U.S. Pat. No. 3,951,297 having the end of the fill tube substantially obstructed by a conical member. Other types of anti-siphoning devices which are inserted within the fill pipe are illustrated in U.S. Pat. Nos. 3,888,381 and 3,920,145.
In each of the devices described above, the anti-siphoning device may be defeated by inserting an elongated element like a rod in the fill tube and applying sufficient force to puncture the obstruction at the end of the fill tube of the anti-siphoning device or to totally destroy the other style of anti-siphoning devices. Similarly, the anti-siphoning devices of the prior art substantially obstruct the flow of fuel through the fill pipe or tube, thereby increasing the amount of time required to fill the tank or container. This is particularly objectionable where the dispensing device or nozzle has an automatic cut off. The obstruction retains the fuel within the fill tube or pipe adjacent the end of the nozzle which continually cuts off.
Thus, there exists a need for an anti-siphoning device which may be readily installed, may not be readily defeated, and which provides for a substantially unobstructed flow of the fuel therethrough.